If your device with iOS 11 unexpectedly restarts repeatedly on or after December 2, 2017, learn what to do.

Try to update your device to iOS 11.2. After you tap Download and Install, the download will continue even if your device restarts. Wait for the update to complete.

If you can't update, turn off notifications for all the apps on your device, then update your device to iOS 11.2:

1. Tap Settings > Notifications.2. Tap an app, then turn off Allow Notifications. Repeat this step for each app.3. Update your device to iOS 11.2.4. After updating, tap Settings > Notifications and turn Allow Notifications on again for each app.